The present invention relates to an assembly for retaining a removable tool bit in place while at the same time allowing it to be manually removed against a biasing force applied to the tool bit by the assembly.
Removable tool bit assemblies must be capable of accommodating rapid insertion and removal of the tool bit without the need for screwing and unscrewing locking assemblies or imparting any other time consuming operation in order to retain and remove the tool bit. One solution as disclosed by U.S. Pat. No. 4,924,733 is to use a magnet in the nosepiece abutting an end of the tool bit when inserted. However, the magnet constitutes and additional expense and assembly step to install. Moreover, magnets can lose their strength and become ineffective, particularly when the make contact only with the pointed end of the bit.
Another common arrangement is a receptacle in a shaft or nose piece into which the bit is inserted until a notch in the tool aligns with a hole in the shaft. A ball bearing slightly larger than the hole in the shaft is held against the hole and extends through the latter to engage the notch by a spring that is held against the ball bearing. The spring is in the form of a split ring with a hole opposite the split so as to impede movement of the ring relative to the ball. One problem with such a device is that the ring often slips off of the ball bearing and turns to the degree that the split straddles the ball bearing. At the latter point it is often the case that the ball will squeeze through the split, drop to the ground and become lost. The screwdriver thus becomes inoperative.
Accordingly, it is an object of the invention to provide an improved assembly for releasably holding a tool bit in place.